This invention relates to a vacuum type circuit interrupter that comprises a flexible metal bellows of generally tubular form that acts as a seal around the movable contact rod of the interrupter. The invention relates more particularly to means for protecting this bellows against possible mechanical damage resulting from operation of the interrupter when the bellows has not retained its normal axial symmetry.
In a vacuum-type circuit interrupter, it is conventional to guide the axially movable contact rod by means of a tubular guide that is located within the above-described flexible tubular bellows. Ordinarily, a rather large clearance is provided between the outside of this guide and the inside of the surrounding bellows. The usual bellows applied in a conventional way has an axial symmetry that it retains both when inactive and when compressed or expanded during operation of the interrupter, and this retention of axial symmetry results in maintenance of the relatively large clearance between the guide and the surrounding bellows.
However, in certain vacuum interrupter applications the ordinary flexible bellows does not effectively retain its normal axial symmetry. One such application is where the pressure differential across the bellows is greater than that for which the bellows is normally designed. This relatively large pressure differential causes the bellows to bow slightly, and this bowing can result in interference developing between the bellows and the guide, which interference can mechanically damage the bellows when the interrupter is operated.